本研究計畫以WRF模式為計算平台，針對都卜勒雷達觀測建立LETKF 資料同化系統，並評估其改善中尺度短期數值天氣(含定量降水)預報之效率及準確度的能力。初期以同化虛擬之都卜勒徑向風資料為主，亦即以 OSSE方式設計數值實驗，後續之計畫則擬逐步增加回波及雙偏極化雷達參數之同化，最後則進一步針對實際觀測資料進行測試。本研究規劃預計執行三年，預期要達到之研究目標如下： (1) 完成雷達徑向風資料觀測算符之撰寫，同化單或多部都卜勒雷達之虛擬風場資料，進行OSSE 實驗，分析此系集資料同化系統於改善對流尺度模式預報之表現。 (2) 發展其他雷達參數之觀測算符，如回波、差異反射率(Zdr)、反射率差 (Zdp)、比差異相位差(Kdp)等；進行OSSE 實驗，比較同化不同參數之表現差異。 (3) 評估WRF模式在不同條件設定（初始化、物理參數化等）下，此系集資料同化系統對各氣象場預報之影響程度。 (4) 評估此系集資料同化系統應用於實際個案之可行性。 This research plans to use WRF (Weather Research and Forecasting) Model as the computational platform, and develop a Doppler radar data assimilation system based on the LETKF (local ensemble transform Kalman filter) method. The ability of this system in terms of improving the efficiency and accuracy of a mesoscale short-range numerical weather prediction (including QPF) will be evaluated. In the early stage of this project, only simulated radial wind data will be assimilated, while reflectivity and other dual-polarimetric parameters are expected to be included in the later stage. Applications to use real observations will also be investigated. This proposal is designed for the next three years, and the research goals are listed in the following: (1) Accomplish the observation operator for the Doppler radial wind data, assimilate simulated radial wind observations from single or multiple Doppler radars in OSSE-type experiments, and analyze the performance of this ensemble-based data assimilation system at convective scales NWP. (2) Develop the observation operators for other dual-polarmetric radar variables, such as reflectivity, differential reflectivity (Zdr), reflectivity difference (Zdp) and specific differential phase (Kdp), and compare the performances of the model forecasts after assimilating these additional radar parameters. (3) Evaluate the WRF-LETKF forecasts of various meteorological variables under different model setups (initialization, physical parameterization, etc). (4) Feasibility study for applications to real cases. 研究期間：9908 ~ 10007
